Polyester fibers have been widely used as fabric materials for clothing by utilizing the excellent properties of the fibers. As diversified and individualized clothing for daily life, and to make high grade clothing for daily life, various attempts have been made to impart preferable properties, that natural fibers have, such as a water-absorbing ability, to polyester fibers.
Furthermore, fabrics having a significantly quick drying property in addition to an enhanced water-absorption have come to be used for the application in sportswear such as athletic shirts or golf wear, so that the sportswear maintains a comfortable wearable state, even when the wearer sweats. For polyester fibers, an improvement in the fibers, in water-absorption and quick drying properties, is desired.
Conventional polyester false-twist textured yarns are rich in bulkiness, exhibit a high tensile strength and a good elongation property, and have excellent easy-care properties and a significant dry touch. The polyester false-twist textured yarns are therefore preferably used for application in clothing. However, attention has been paid in recent years to false-twist textured yarns excellent in a water-absorbing ability and the feeling given to the wearers. Demand for materials having a sweat-absorbing property and a quick drying property has been increasing in applications such as sportswear, shirts for soccer and athletic shirts in order for the sportswear to maintain a comfortable wearable state even when the wearers sweat.
However, synthetic fibers such as polyester fibers used as materials for false-twist textured yarns generally have a low water-absorbing ability, and therefore have the problem that they give an uncomfortable feeling to the wearers in applications in which they are directly contacted with the skin. A solution to the problem is therefore desired.
There is such a known method that imparts a water-absorbing ability to a polyester fiber as disclosed in Japanese Examined Patent Publication (Kokoku) No. 61-31231. The method comprises producing a hollow fiber from a polyester resin containing a sulfonic acid compound, and alkali treating a fabric prepared therefrom so that the sulfonic acid compound is eluted to form fine pores in the fiber cross-sectional profile, which fine pores impart a water-absorbing property to the polyester fibers. Moreover, Japanese Unexamined Patent Publication (Kokai) No. 54-151617 proposes a method wherein an oriented polyester yarn (called a flat yarn) having fiber cross-sectional profiles with slots and/or arm-like protrusions is produced from a polyester containing a metal sulfonate salt, and a water-absorbing fabric is produced therefrom. However, when such a hollow fiber or an oriented polyester yarn having cross-sectional profiles with slots and/or arm-like protrusions is false-twist textured, hollow portions, slots and arm-like protrusions are crushed. Consequently, there is no difference between the fiber cross-sectional profiles subsequent to false-twist texturing and those of a conventional false-twist textured yarn. A fabric produced from such a polyester false-twist textured yarn shows no adequate water-absorption even when treated with alkali. Moreover, when a fabric is formed from the hollow polyester fibers in a flat yarn form without false-twist texturing, the fabric manifests a water-absorption when treated with alkali. However, the fabric shows a poor moisture dissipation property, and the wearer has a wet and uncomfortable feeling after sweating.
Japanese Examined Patent Publication (Kokoku) No. 61-31232 discloses a method comprising false-twist texturing a polyester conjugate fiber having a core-in-sheath structure, producing a fabric therefrom, and alkali treating the fabric to elute a polyester in the core portion. However, production of a flat yarn having such a complicated structure is extremely difficult. The polyester false-twist textured yarn thus obtained becomes extremely expensive, and wide commercial use of the yarn is difficult.
Furthermore, Japanese Examined Patent Publication (Kokoku) No. 62-45340 and Japanese Patent Publication No. 2667152 disclose a technology, as a method of imparting a sweat-absorbing property and a quick drying property to a synthetic fiber fabric, wherein a multilayered structure fabric is produced from polyester fibers having concavities in fiber cross-sectional profiles, and absorbed water is introduced into gaps among the constituent individual fibers so that the quick drying property of the fabric is made significant. However, production of a fabric having such a special structure is costly, and the range of use is restricted. Moreover, when a polyester fiber having concavities in the fiber cross sectional profiles is false-twist textured, the cross-sectional profiles of the fibers are greatly deformed, and capillary gaps among individual fibers that bring about a capillary effect are often not formed.
Furthermore, Japanese Unexamined Patent Publication (Kokai) No. 11-269718 discloses a polyester false-twist textured yarn with a W-shaped cross section which has a fiber cross-sectional profile in a specific scope after false-twist texturing, and the water-absorption of which is not impaired. However, even when a polyester fiber having a W-shaped cross section that has heretofore been widely disclosed as a typical cross-sectional shape of a water-absorbing polyester fiber is false-twist textured by a known method, manifestation of sufficient water-absorption and quick drying property cannot be expected.
As explained above, a polyester false-twist textured yarn constituted from polyester fibers that have a highly irregular cross section, prepared by false-twist texturing the polyester fibers, and suitable for producing a fabric that manifests sufficient water-absorption and quick drying properties, and a process for producing the same are unknown.